The present application relates generally to methods and compositions for the repair or regeneration of damaged or diseased cells or tissue. Several embodiments relate to administration of exosomes (or protein and/or nucleic acids from the exosomes) isolated from cells or synthetic surrogates in order to repair and/or regenerate damage or diseased tissues. In particular, several embodiments, relate to exosomes derived from certain cell types, such as for example cardiac stem cells, and use of the exosomes in the repair and/or regeneration of cardiac tissue.